The present invention relates to elongated, generally prismatic or cylindrical elements, made of pre-stressed concrete, which, by a simple arrangement, may be assembled end to end.
It is known that mass-production of elongated elements of pre-stressed concrete, especially those whose section is relatively small, is advantageously obtained with adherent reinforcements; to this end, the reinforcements are initially tensioned and the concrete is cast in shutterings through which these tensioned reinforcements pass; after the concrete has set, the connections of the reinforcements with the tensioning members are released which, by adherence, transfers the force of tension of the steel reinforcements to the concrete. Operation generally takes place on "long forms", of the order of one hundred and fifty meters, along which are disposed series of moulds through which pass, in file, the tensioned reinforcements from the ends of the form. After setting and hardening of the concrete, the reinforcements are cut between the moulds at right angles to the penetration thereof in the cast pieces.
it is difficult and delicate operation to assemble two concrete elements thus produced end to end without loosing the efficacy of the pre-stress on either side of the assembly. In fact, it is known that the complete tension of the or each reinforcement is re-established, after they have been cut at right angles to one face of the element, only to a certain depth (for example 10 to 20 cm) inside this element. The end of the element is therefore not pre-stressed. Moreover, after cutting, the anchoring of the reinforcements results, at these ends, only from the increase in their section due to the loss of the tension which drew them; in the case of alternate efforts, the loss of tension may propagate towards the inside of the element, increasing the length thereof which is not pre-stressed.
Finally, this weakening of the ends renders the end-to-ends assembly of the elements, for example sections of piles, even more precarious.
One known way of overcoming these drawbacks consists in providing the ends of such elements with steel plates through which the tensioned reinforcements pass at manufacture and which comprise, towards the inside of the element, sections of ordinary reinforcements welded to the inner face of these plates. These complementary reinforcements reinforce the non-prestressed ends of the element whilst the plates may facilitate end-to-end assembly of the elements.
The invention provides an improved solution to this problem.